Time series of tropical Atlantic and East Pacific GOES IR imagery, every 12 hours (at ~00Z and ~12Z) from 20-30°N, newest on top. Updated 10am and 10pm EDT. Images courtesy of NRL-MRY. To estimate the speed of a propagating feature, if it moves toward the left in subsequent frames (looking upward) at 10°/frame, that's approximately 50kts. If it takes two frames to traverse 10°, it's moving at about 25kts, etc.